Day51 图论part02

99.岛屿数量 深搜

注意深搜的两种写法，熟练掌握这两种写法 以及 知道区别在哪里，才算掌握的深搜。

代码随想录

方法1：加终止条件

import java.util.Scanner;

public class Main{
    public static int[][] dirc = new int[][]{
   
   {0,1} ,{1,0},{-1,0},{0,-1}};
    
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        
        int[][] graph = new int[n][m];
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                graph[i][j] = scanner.nextInt();
            }
        }
        
        boolean[][] visited = new boolean[n][m];
        
        int res = 0;
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                if(visited[i][j] == false && graph[i][j] == 1){
                    res++;
                    dfs(visited, graph, i , j);
                }
            }
        }
        
        System.out.println(res);
    }
    
    public static void dfs(boolean[][] visited, int[][] graph, int x, int y){
        if(!(x >= 0 && x < graph.length && y >= 0 && y < graph[0].length)){
            return;
        }
        if(!(visited[x][y] == false && graph[x][y] == 1)){
            return;
        }
        visited[x][y] = true;
        for(int i = 0; i < dirc.length; i++){
            int nextx = x + dirc[i][0];
            int nexty = y + dirc[i][1];
            dfs(visited, graph, nextx, nexty);
        }
    }
    
}

方法2:不加终止条件

import java.util.Scanner;

public class Main{
    public static int[][] dirc = new int[][]{
   
   {0,1} ,{1,0},{-1,0},{0,-1}};
    
    public static void main (String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        
        int[][] graph = new int[n][m];
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                graph[i][j] = scanner.nextInt();
            }
        }
        
        boolean[][] visited = new boolean[n][m];
        
        int res = 0;
        for(int i = 0; i < n; i++){